Ansible Pilot

Concatenate multiple files in a specific order - Ansible module template and YAML

How to automate the concatenation of multiple files and format using a list in the YAML and Ansible module template with Jinja2 language. Included example with "a.txt", "b.txt" and "includes.yaml" files for Pandoc.

How to use Concatenate multiple files in a specific order using Ansible?

This is extremely useful for service configuration files, reports, and so much more use cases. I personally use this code for markdown documents for Pandoc. I’m going to show you a live demo with some simple Ansible code. I’m Luca Berton and welcome to today’s episode of Ansible Pilot.

Ansible Concatenate multiple files in a specific order

Let’s talk about the Ansible module template. The full name is ansible.builtin.template, it’s part of ansible-core and is included in all Ansible installations. It templates a file out to a target host. Templates are processed by the Jinja2 templating language. Also you could use also some special variables in your templates: ansible_managed, template_host, template_uid, template_path, template_fullpath, template_destpath, and template_run_date. It supports a large variety of Operating Systems. For basic text formatting, use the Ansible ansible.builtin.copy module or for empty file Ansible ansible.builtin.file module. For Windows, use the ansible.windows.win_template module instead.

Parameters

Let me highlight the most useful parameters for the template module. The only required parameters are “src” and “dest”. The “src” parameter specifies the template file name. Templates usually are stored under “templates” directories with the “.j2” file extension. The “dest” parameter specifies the path where to render the template on the remote machine. The “validate” parameters allow you to specify the validation command to run before copying it into place. It’s very useful with configuration files for services. Please note that the special escape sequence “%s” is going to be expanded by Ansible with the destination path. If the “backup” parameter is enabled Ansible creates a backup file including the timestamp information before copying it to the destination. Let me also highlight that we could also specify the permissions and SELinux properties.

demo

How to concatenate multiple files in a specific order with the Ansible module template and YAML.

code

A content
B content
input-files:
  - concatenate/b.txt
  - concatenate/a.txt
---
- name: concatenate demo
  hosts: "{{ HOSTS }}"
  become: false
  gather_facts: true
  vars:
    myinput: "concatenate/includes.yaml"
    myoutput: "concatenate/output.txt"
  tasks:
    - name: include file list
      include_vars:
        file: "{{ myinput }}"
        name: files

    - name: concatenate
      ansible.builtin.template:
        src: templates/concatenate.j2
        dest: "{{ myoutput }}"
{% for i in files["input-files"] %}
{{ lookup('file', i) }}
{% endfor %}

execution

ansible-pilot $ ansible-playbook -e "HOSTS=localhost" concatenate.yml 
[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit
localhost does not match 'all'
PLAY [concatenate demo] ***************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [localhost]
TASK [include file list] **************************************************************************
ok: [localhost]
TASK [concatenate] ********************************************************************************
changed: [localhost]
PLAY RECAP ****************************************************************************************
localhost                  : ok=3    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
ansible-pilot $

idempotency

ansible-pilot $ ansible-playbook -e "HOSTS=localhost" concatenate.yml
[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit
localhost does not match 'all'
PLAY [concatenate demo] ***************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [localhost]
TASK [include file list] **************************************************************************
ok: [localhost]
TASK [concatenate] ********************************************************************************
ok: [localhost]
PLAY RECAP ****************************************************************************************
localhost                  : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
ansible-pilot $

before execution

ansible-pilot $ ls -al concatenate
total 24
drwxr-xr-x  5 lberton  staff  160 Feb  1 15:40 .
drwxr-xr-x  9 lberton  staff  288 Feb  1 15:08 ..
-rw-r--r--  1 lberton  staff    9 Feb  1 15:18 a.txt
-rw-r--r--  1 lberton  staff    9 Feb  1 15:18 b.txt
-rw-r--r--  1 lberton  staff   56 Feb  1 15:48 includes.yaml
ansible-pilot $ cat concatenate/a.txt
A content%
ansible-pilot $ cat concatenate/b.txt 
B content%
ansible-pilot $ cat concatenate/includes.yaml 
input-files:
  - concatenate/b.txt
  - concatenate/a.txt
ansible-pilot $

after execution

ansible-pilot $ ls -al concatenate
total 32
drwxr-xr-x  6 lberton  staff  192 Feb  1 15:50 .
drwxr-xr-x  9 lberton  staff  288 Feb  1 15:08 ..
-rw-r--r--  1 lberton  staff    9 Feb  1 15:18 a.txt
-rw-r--r--  1 lberton  staff    9 Feb  1 15:18 b.txt
-rw-r--r--  1 lberton  staff   56 Feb  1 15:48 includes.yaml
-rw-r--r--  1 lberton  staff   20 Feb  1 15:49 output.txt
ansible-pilot $ cat concatenate/output.txt 
B content
A content
ansible-pilot $

code with ❤️ in GitHub

Recap

Now you know how to concatenate multiple files in a specific order with the Ansible module template and YAML. Subscribe to the YouTube channel, Medium, Website and Twitter to not miss the next episode of the Ansible Pilot.

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February 1, 2022

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